Vehicle leaf springs



Feb. 21, 1967 1 G. BouGl-INER ETAL 3,305,231

VEHICLE LEAF SPRINGS Filed Nov. 16, 1964 2 Sheets-Sheet 1 A/30 .f3-T4 E INVENToRs LAWRENCEaoz/@HNER @USL/20u05 4ATTORNEYS Feb. 2l, 1967 L.. G. BOUGHNER ETAL 3,305,231

VEHICLE LEAF SPRINGS Filed Nov. 16, 1964 2 Sheets-Sheet 2 INVENTORS LAWRENGEG. BOUGHNER GUS L. POU/.05

ATTORNEYS United States Patent C) 3,305,231 VEHICLE LEAF SPRINGS Lawrence G. Boughner, Birmingham, and Gus L. Poulos,

Rochester, Mich., assignors to Rockwell-Standard Corporation, Pittsburgh, lia., a corporation of Delaware Filled Nov. I6, 1964, Ser. No. 411,285 I3 Claims. (Cl. 267-52) The presen-t invention refers to vehicle spring suspensions and more particularly to vehicle leaf spring sus- .pensions for single axles or for tandem axle bogies.

In leaf spring suspensions it has ybeen commercial practice to provide the individual leaves in a niultileaf assembly with a center hole by which the leaves are clamped together by means of a through bolt to form a unit ready for convenient shipping. The center bolt is retained in the multileaf assembly after installation on the vehicle :and serves as a convenient means to center the leaves and prevent their longitudinal or transverse displacement relative to each other.

In single tapered leaf spring suspensions which more recently have come into widespread use, it has also been the practice to provide the leaf with such :a center hole which serves to center the leaf at the seat area and prevent it from longitudinal or transverse movement. These familiar center bolt holes serve the further purpose of properly locating the leaf at various workstations during their manufacturing, and in general they have become regarded as of vital importance -for convenient handling and mounting of the spring leaves.

It is known from :analytical study of spring leaves, which are essentially cantilever beams, that maximum stress occurs at the clamping area, and it was early recognized that any reduction in met-al cross section area at that area, as by a bolt hole, would result in a material increase of localized stresses which would enhance the possibility of early failure. In practice, most leaf spring failures have correspondingly occurred at or near the seat or clamping area.

Attempts have heretofore been made to compensate for the reduction in material due to the center bolt holes by adding separate clamping and reinforcing plates to the leaf or multi-leaf pack at the seat area, between which plates the leaves are sandwiched to materially increase the metal cross section at that 'area in an attempt to reduce the localized stresses set up therein. This expedient, however, added to overall costs and increased the unsprung weight, both undesirable in vehicle suspension design.

Attempts have also Ibeen rnade to eliminate the center hole entirely and provide intertting integral dimples and notches in the adjacent leaves at the seat area. Such an assembly is clamped together by a metal band or strap and `thus the interlocked dimples :and notches provide a locat-ing and centering means for a multi-leaf spring unit as disclosed in the United States Patent No. 245,097 to E. Spaulding, dated August 2, 1881. Other similar proposals in attempted solution of the problem provided recesses at the side surfaces of the leaf and cooperating projections in the clamping band or seat bracket adapted to iit into these recesses to lock the leaves together.

It is difficult to exactly locate, align and stamp out such recesses vand/or projections in the spring leaves for Iany one multi-leaf unit, and proper relative location of the leaves is very important to obtain the designed spring rate in an assembly. Furthermore, where the projections and recesses in the spring leaf are provided respectively at the tension and compression surface of the spring leaf, the stamping process required to produce the recess in one surface results in a projection extending ICC from the opposite surface and this materially weakens the leaf at that point in almost the same degree as if la center hole was provided.

Another proposed attempt to center and locate the spring leaves in relation to each other and upon the spring seat was to provide opposite vertical semi-circular notches in the sides of the leaf or leaves in which a U-bolt of the clamping bracket would fit to laterally and longitudinally center the leaf or leaves :and prevent them from displacement. However, the removed metal required to form two matching semi-circular notches in the leaf is such that the effect is practically the same as if a center hole was provided so that this does not solve the problem.

Another prior method consisted in materially enlarging or widening the spring leaf at the seat clamping area to form tangs or wings which are bored to receive the clamping bolts. Although in this prior method the locating and clamping holes are outside of the clamping area thus providing a full uninterrupted cross section Within the clamping area, the manufacture of such leaf spring construction is extremely diicult and costly due to the side extensions at the clamping area of the leaf which have to be precisely rolled out from the material of the leaf while maintaining the leaf characteristics, requiring special dies and rolling machines. In addition, there is a considerable undesirable increase in unsprung weight when this method is adopted.

'Ilhe present invention provides a novel spring leaf construction that overcomes the foregoing disadvantages encountered in prior attempts to eliminate the center hole leaf springs and multi-leaf spring assemblies. The invention does not materially weaken the leaf or appreciably increase the weight of the spring and it can [be easily manufactured at less cost than prior methods mainly using present equipment. In addition, the present invention provides a convenient handling and location means for the leaf during the various stages of manufacture as well :as a convenient means for assembling and securing a stack of spring leaves together for shipping, so that it provides advantages equivalent to the `center hole w-ithout the disadvantages of the latter.

With the foregoing considerations in mind, the present invention comprises means exemplified in the various` emhodiments `described in the following description with reference to the attached drawings forming part of the specification wherein:

FIGURE 1 is a fragmentary side elevation, partially broken away and in section illustrating the spring seat arrangement of a dual leaf spring assembly for a tandem bogie equipped according to a preferred embodiment of the invention;

FIGURE 2 is an end view partly broken away and in section substantially .along line 2-2 of FIGURE l;

FIGURE 3 is a side elevation illustrating the dual leaf spring assembly of FIGURE l separate from the vehicle and clamped in assembly for shipment.

FIGURE 4 is a fragmentary end view partially broken away and in section substantially along line 4 4 of FIGURE 3;

FIGURE 5 is la fragmentary end elevation partly in section showing a tandem bogie suspension spring seat arrangement of another embodiment of the invention;

FIGURE 6 is a side elevation illustrating handling of the spring leaf of the invention during manufacture;

FIGURE 7 is an enlarged section through FIGURE 6 showing one type of spring handling means; and

FIGURE 8 is a view similar to FIGURE 7 illustrating another mode of handling the spring leaf.

FIGURES 1 and 2 show the invention as embodied in a tan-dem axle bogie suspension having a central tubular cross member that extends parallel to and intermediate the transverse axles (not shown). Tube 20 provides a rocking pivot for the leaf spring assemblies 22 disposed at opposite sides of the frame. Each spring assembly 22 comprises two substantially identical superposed formed steel spring leaves 24 and 26. Lower leaf 26 rests on the arcuate saddle surface 28 of a spring seat bracket 30 which may be attache-d to or integral with the pivotally mounted cross tube 20. Surface 28 may be flat or slightly curved to accommodate the camber formation of the leaf spring assembly 22 which is secured to the seat bracket 30 as by a top pressure plate 32 overlying upper leaf 24 and U-bolts 34 that extend through bracket 30 and carry nuts 35 whereby the entire assembly is clamped to the seat bracket. To reduce fretting, liners 36 of a hard smooth plastic such as Delrin (trademark) or a similar composition may be placed between the leaves and between the lower leaf 26 and saddle surface 28, and between the upper leaf 24 and the pressure plate 32. The opposite ends of the spring assembly 22 are suitably connected to the axles of the bogie (not shown).

The general tandem vehicle suspension spring seat arrangement so far described herein is more or less conventional and does not form a part of the present invention. The dual taper leaf spring assembly may for example be that disclosed in Hallam Patent No. 3,053,527 issued September 1l, 1962.

The spring leaves 24 and 26, which may be taperrolled as shown or conventionally of uniform thickness, do not have the customary center bolt hole but instead each is provided midway between its ends, that is, at the seat area (which in taper-rolle-d leaves is the area of maximum thickness) with two oppositely projecting studs 38 welded one each to the outer side 40 and inner side 42 of the respective leaves. These rigid side studs 38, although preferably cylindrical as shown, may be of any other desired cross section. Side studs 38 are positioned on the neutral axis of the leaf, that is, the axis of each stud is an equal distance from either tension surface or compression surface 27 of its leaf. Studs 38 do not in any way interrupt the continuity of the tension or compression surfaces of the spring leaves.

The studs 38 are of suicient length to enable them to extend into vertical slots 44 formed in upright lugs 46 of the seat bracket on Iboth sides of the leaf spring assembly. Slots 44 are located substantially on the vertical centerline of cross tube 20.

The spring leaves 24 and 26 are longitudinally centralized in the assembly and prevented from longitudinal movement relative to each other by the foregoing stud and slot arrangement, and they are laterally confined by the lugs 44 and the U-bolts. There is no objectionable center bolt hole, and a full cross section of metal is provided at the spring seat area which considerably increases the ability of the spring to absorb the high stresses usually found at the clamping section of a leaf spring.

The amount of material represented by studs 38 is of negligible weight and does not affect the designed spring rate. Furthermore, the leaves are easily assembled and centralized on the spring seat 30, since the side studs 38 need only be dropped slidably into slots 44 and are retained therein without the use of any special fasteners.

FIGURES 3 and 4 show the dual spring leaf assembly 22 of FIGURES 1 and 2 separate from the vehicle, as it would appear for storage and shipment. The leaves 24 and 26 are held in assembly by two flexible metal side straps 47 having apertures 48 spaced a distance corresponding to the distance between the side studs 38 on adjacent leaves 24 and 26. These straps 47 at each side are pressed over the studs 38 thus clamping the two leaves 24 and 26 together without the use of fasteners. Due to the separating force between the two leaves 24 and 26 because of their different camber the straps 47 are securely held in place on the studs 38 and will not slip off during handling of the leaf assembly. It will, of course,

be understood that any desired number of leaves may be assembled in the same fashion in a multi-leaf assembly.

The assembly straps 47 may remain in `place when the spring is installed in the vehicle as shown in FIGURE 4 to provide additional locating and holding means for the spring assembly. The inner sides of spring seat bracket lugs 46 are here provided with vertical grooves 45 that face each other to receive the side straps 47, thus cooperating with studs 38 and notches 44 in accurately locating and centering the spring assembly 22. This arrangement eliminates need for disassembly of the spring unit during installation or when it is removed for repair reasons.

FIGURE 5 illustrates an embodiment wherein separate side studs lit into corresponding small side recesses in the side surfaces of the spring leaf. The single taper leaf spring suspension here illustrated is preferably that disclosed in Hallam Patent No. 3,145,984 issued August 25, 1964.

Member 20 represents a cross member in a tandem axle assembly as in FIGURE 1 or it may represent a vehicle axle housing or axle beam which is provided with a spring seat 'bracket S8 having a saddle surface 52 which may be fiat or slightly curved to accommodate the camber formation of a leaf spring 54 resting thereupon. A hard plastic liner 56 may be provided between the leaf 54 and the saddle S2 to prevent fretting of the adjoining surfaces during spring articulation.

The leaf 54, in this instance, is provided at its seat area, that is, at the area of maximum thickness in a tapered leaf, with recesses 58 punched or pressed into the opposite side surfaces 60 and 62 of the spring leaf at the neutral axis thereof, equidistant between the tension and compression surfaces.

These recesses, which may be of any desired cross section, are of suiiicient depth to accommodate one end of studs 64 which project freely within apertures 66 of rigid vertical bracket lugs 68 at the sides of the leaf. Lugs 68 may be welded to or integral with the seat bracket 50. Removable cotter pins 70 or like fasteners extending through studs 64 in the spaces between the spring leaf and the lugs 68 prevent the studs 64 from sliding out of the recesses in the spring or the apertures in the brackets 68.

It will be understood that any desired number of associated spring leaves may `be assembled together to form a multi-leaf unit of desired spring rate `by extending lugs 68 and providing a corresponding number of recesses 58, apertures 66 and studs 64. The spring leaf or leaves in this instance also are secured to the seat 52 by the usual pressure plate and U-'bolts (not shown), as illustrated in FIGURE 1.

The construction in FIGURE 5 even though the recesses 58 remove a small but insignificant amount of metal cross section in the spring seat area may be sometimes preferred from a manufacturing point of view, because the recesses 58 in the sides of the leaf may -be used for handling and gaging purposes during manufacturing as was formerly done with the conventional center bolt hole. This configuration will also be preferred where it is technically difficult or impracticable to weld studs 38 to the sides of the leaf spring.

Since recesses 58 are on the neutral axis of leaf 54 and of relatively small size compared to the width and thickness of the leaf and since, as in the embodiment of FIG- URES 1-4, both the tension surface 53 and compression surface 55 of the leaf remain unbroken these recesses 58 do not adversely affect the fatigue life of the leaf.

FIGURES 6 to 8 show by way of example the handling of spring leaves during manufacture using the novel locating and centering arrangement provided by the invention.

FIGURES 6 and 7 illustrate the handling of spring leaf 24 provided with projecting side studs 38 as in FIG- URES l to 4, and FIGURE 8 illustrates the handling of a spring leaf 54 yprovided with side recesses 58 such as illustrated in FIGURE 5.

Referring to FIGURES 6 and 7, the spring leaf 24 is provided with the welded-on side studs 38 at an early stage in the manufacturing operation, such as after the leaf has been tempered. The various subsequent work operations in the manufacturing of spring leaves requires handling and transporting of the spring leaf from one work station to another, as for instance in FIGURE 6 in which the spring leaf 24 may be suspended from an overhead conveyor (not shown). To this end a tongtype gripping tool 102 may be applied to the leaf 24 with its apertured arms 104 and 106 conveniently fitting over the side studs 38 at the center of the spring. Thus the side studs 38 provide a convenient handling means for transport during further manufacture of the spring which include a variety of operations not further illustrated here since they are well known in spring manufacture.

In FIGURE 8 the same type of handling is illustrated involving a spring leaf 54 having side recesses 58 such as illustrated in FIGURE 5. In this instance, the arms 112 and 114 of the tongtype tool 102 are provided with opposed projections 103 which extend into the side recesses 58 of the leaf 54, thereby securely gripping the leaf. Thus, the side recesses also provide a convenient handling means during transfer from one work station to another.

One of the work operations in the manufacture of leaf springs is the so-called Bull-Dozing by which the cambered leaf is deflected beyond its normal rate of load deflection to give the leaf spring a permanent set. Using the present invention this important operation is greatly improved since the side studs permit full Bull-Dozing without the use of a supporting center clamp which is otherwise necessary in a conventional leaf provided with a centerhole `to prevent yielding at the center bolt hole area at a lower stress point than the desired load stress. Side studs 38 and recesses 58 also provide convenient gage location points for locating the leaf for work operations such as endforming.

The fatigue life of any single leaf spring especially in regard to the seat area has been found to be much longer than in leaves provided with the conventional center bolt holes, as documented by extensive test data.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be Considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. In a vehicle spring suspension, a metal spring leaf having tension and compression surfaces of uninterrupted continuity, a mounting bracket for said spring leaf, said spring leaf having a longitudinally intermediate portion where one of said surfaces is seated on said bracket, interfitting side stud and recess means at laterally adjacent sides of sai-d bracket and said spring leaf vertically intermediate said surfaces for longitudinally and laterally locating s-aid spring leaf in the suspension, and fastening means independent of said stud and recess means for securing said intermediate portion of the spring leaf to said bracket, whereby said spring leaf is mounted on sai-d bracket without interrupting the continuity of said tension and compression surfaces.

2. In a vehicle spring suspension as defined in claim 1, said studs being rigid projections from opposite sides of said spring leaf and said recesses being formed in bracket extensions on opposite sides of said spring leaf for freely receiving said studs.

3. In a vehicle spring suspension as defined in claim 2, said recess being ope-n at the top :for slidably receiving said studs when the suspension is assembled.

4. In a vehicle spring suspension 'as defined in claim 6 2, said studs being weld-on projections on the sides of said spring leaf.

5. In a vehicle spring suspension as defined in claim 1, said recesses being formed in the sides of said spring leaf and said studs being mounted on extensions of said bracket at opposite sides of said spring leaf.

6. In a vehicle spring suspension, a multileaf spring assembly comprising a plurality of superposed metal spring `leaves each having tension and compression surfaces of uninterrupted continuity, a mounting bracket for said spring assembly, said assembly having a longitudinally intermediate portion mounted on said bracket, interftting side stud and recess means at laterally Iadjacent sides of said bracket and each -of said spring leaves vertically intermediate said surfaces of lthe respective leaves for laterally and longitudinally locating said spring leaves in the suspension, and iioating means independent of said stud and recess means for securing said intermediate portion of the spring assembly to said bracket, whereby said spring leaves are mounted on said bracket Without interrupting the continuity of said spring leaf tension and compression surfaces.

7. In the vehicle spring suspension defined in claim 6, said studs being rigid projections extending from opposite sides of said spring leaves and freely received in said recess means.

8. In the vehicle spring suspension defined in claim 6, said studs being rigid side projections on each of said spring leaves, 'and said bracket havin-g opstanding lugs at opposite sides of said assembly with each lug being formed with a recess common to all of the studs on the adjacent side of said `assembly.

9. In the vehicle spring suspension defined in claim 8, side straps connecting the lstuds on each side of said assembly, and grooves on the inner sides of said lugs receiving said straps in the assembly.

10. In the vehicle spring suspension defined in cl-aim 8, said lug recesses being open at the top to slidably receive said lugs during assembly.

1-1. In a vehicle spring suspension, a metal spring leaf having tension and compression surfaces of uninterrupted continuity, a mounting bracket for said spring leaf, said spring leaf having a longitudinally intermediate portion seated on said bracket, rigid lateral studs projecting oppositel'y from the sides of said spring leaf substantially midway vertically intermediate said surfaces, recess means in laterally adjacent side extensions of said bracket for slidably receiving said studs and thereby locating said spring leaf longitudinally and laterally in the suspension, and fastening means independent of said stud and recess means for securing said intermediate portion of the spring -leaf to said bracket, whereby said spring leaf is mounted on said bracket with-out interrupting the continuity of said spring :leaf tension and compression surfaces.

12. In a vehicle spring suspension, a metal spring leaf having tension yand compression surfaces of uninterrupted continuity, a mounting bracket for said` spring leaf, said spring leaf having 'a longitudinally intermediate portion seated on said bracket, opposed recesses in Opposite sides of said spring leaf substantially midway vertically intermediate said surfaces, studs mounted on opposite side extensions of said bracket and projecting freely into said spring leaf recesses for laterally and longitudinally locating said spring leaf in the suspension, and fastening means independent of said studs and recesses for securing said intermediate portion of the spring leaf to said bracket, whereby said spring leaf is mounted. on said bracket Without interrupting the continuity of said spring leaf tension and compressi-on surfaces.

13. In the vehicle spring suspension defined in claim 12, said studs being separate elements freely received in said recesses |and aligned apertures in said bracket side extensions, and means for holding the studs in assembly in said suspension.

(References on following page) 7 8 References Cited by the Examiner 1,208,990 12/ 1916 Laycock 267-52 1,275,744 8/1918 Roder 267-52 UNITED STATES PATENTS 1,327,750 1/1920 Wolff 267-52 828,357 8/1906 Wough 267-52 l 1,076,961 10/1913 Doble 267 52 5 ARTHUR L. LA POINT, Pllma'y Exmllel'. 1,174,118 3/1916 Brodecky 267-52 R. H. WOHLFARTH, Assistant Examiner. 

1. IN A VEHICLE SPRING SUSPENSION, A METAL SPRING LEAF HAVING TENSION AND COMPRESSION SURFACES OF UNINTERRUPTED CONTINUITY, A MOUNTING BRACKET FOR SAID SPRING LEAF, SAID SPRING LEAF HAVING A LONGITUDINALLY INTERMEDIATE PORTION WHERE ONE OF SAID SURFACES IS SEATED ON SAID BRACKET, INTERFITTING SIDE STUD AND RECESS MEANS AT LATERALLY ADJACENT SIDES OF SAID BRACKET AND SAID SPRING LEAF VERTICALLY INTERMEDIATE SAID SURFACES FOR LONGITUDINALLY AND LATERALLY LOCATING SAID SPRING LEAF IN THE SUSPENSION, AND FASTENING MEANS INDEPENDENT OF SAID STUD AND RECESS MEANS FOR SECURING SAID INTERMEDIATE PORTION OF THE SPRING LEAF TO SAID BRACKET, WHEREBY SAID SPRING LEAF IS MOUNTED ON SAID BRACKET WITHOUT INTERRUPTING THE CONTINUITY OF SAID TENSION AND COMPRESSION SURFACES. 